1. Field of the Invention
This invention relates to the detection of fumes, odors and the like and has particular reference to a device and method for detecting explosive fumes in the lower portions of an engine driven boat.
2. Description of the Prior Art
It is well known that power driven boats, particularly those propelled by engines using gasoline or similar volatile and explosive fuels, present a potentially dangerous situation in that any fumes resulting from fuel escaping from the engine, fuel tanks, etc., or escaping during the process of fueling, tend to settle in the lower portion of the boat hull and may readily explode if ignited by a spark, open flame or the like.
Fume detectors for detecting explosive fumes have been employed for many years for the purpose of sounding an alarm when such fumes exist. However, such detectors are relatively expensive and are not reliable and often cannot distinguish between explosive and non-explosive fumes. This is substantiated by the Coast Guard and other experts in the field who have repeatedly shown that the human nose is a far more sensitive and reliable sensor than any electrical or other type of fume or odor detector.
The Coast Guard generally advocates using one's nose directly to check for explosive fumes in a boat. This procedure is not generally followed by boat owners, however, because of the inconvenience in doing so. One must normally lift the engine hatches or floorboards and then physically lower himself into the lower portions of the boat to properly detect explosive fumes. This is a tedious, time consuming and often dirty job. Also, the engine, fuel tanks and the like may be so located within an engine compartment, etc., that it is physically impossible for one to lower his head sufficiently to detect fumes collected at the bottom of the boat. Further, it may be extremely dangerous to lower one's self into an engine compartment while the engine is operating.
On the other hand, it is known that fumes are produced by molecules of gas which are released into the air from a volatile substance. When such gas molecules reach the olfactory nerve cells in the upper reaches of each of the two nasal cavities, they stimulate the latter to generate a sensation of smell within the brain. The greater the number of gas molecules and the greater the velocity of a current of air carrying such molecules through the nose and past the olfactory nerve cells, the more intense the smell sensation becomes.
However, man's sense of smell is rather poorly developed compared to that of certain insects and animals. This is, to some extent, due to the fact that the olfactory nerve cells are located in small areas which are mainly out of the path of most of the air transmitted through the nose to the lung. Because of this arrangement, under normal breathing conditions, only about two percent of the air being breathed reaches the olfactory nerve cells and, therefore, only a small portion of odor molecules carried by air being inhaled is detected.